1. Field of the Invention
The present invention relates to a method for selectively arranging ferritin.
2. Related Art
Fine particles (inorganic particles) which include a protein and an inorganic substance and which are arranged on a base material have attracted attention in industrial fields of catalysts, sensors, biochips, transistors, semiconductors lasers, magnetic discs, displays and the like. In particular, patterning techniques have been desired in which inorganic particles are selectively arranged in a specified region, or they are regularly arranged in a fine region of nano-size, when the inorganic particles are industrially applied. Furthermore, in recent years, aiming at miniaturization of total analysis systems including biosensors, applications to fine chemical substance analysis systems (Micro Total Analysis System (μTAS)) have also attracted attention. Behind such a situation, advantages such as improvement of biocompatibility, enablement of lowering of the cost by mass productivity and measurement in the place (portable) and the like are involved.
Techniques for selectively arranging proteins or inorganic particles on a solid surface involve extraordinary difficulty because it is very difficult to allow the surface of the protein and the inorganic substance to have a self-recognizing function. Known methods for forming a fine pattern using a protein that is a biomolecule include a method in which photolithography is utilized (see, A. S. Blawas, W. M. Reichert, Biomaterials, 19, 595 (1998)), microcontact printing (see, A. Bernard, J. P. Renault, B. Michel, H. R. Bosshard, E. Delamarche, Adv. Mater., 12, 1067), dip-pen nanolithography (see, K. B. Lee, S. J. Park, C. A. Mirkin, J. C. Smith, M. Mrksick, Science, 295, 1702 (2002)), and the like. However, in light of mass productivity and costs, techniques for carrying out patterning of fine particles in a nano-size region have been demanded.
Furthermore, a method for regularly arranging nano-size fine particles surrounded by protein molecules is disclosed in Japanese Patent Provisional Publication No. H11-204774. In these methods, procedures of: subjecting the surface of a SAM membrane (self-assembled monomolecular membrane), an LB membrane (monomolecule accumulating membrane) or the like to a processing for selectively arranging the fine particles; executing patterning of the fine particles through further conducting photolithography in combination; forming a region in which the inorganic particles are selectively arranged on the surface of a base material by direct drawing or the like of a pattern on the base material with a nanoprobe such as AFM (Atomic Force Microscope) or the like; and thereafter arranging the inorganic particles.
Hereinafter, a method for arranging inorganic particles using an LB membrane (PBLH membrane) according to the conventional method (Japanese Patent Provisional Publication No. H11-204774) is illustrated in FIGS. 1A to 1H.
First, in the step shown in FIG. 1A, a buffer 11 is reserved in a water bath 10 made of Teflon (registered trade name), and native ferritin 21 including an inorganic particle 20 therein is dispersed in this buffer.
Next, in the step shown in FIG. 1B, a PBLH membrane 30 is overlaid on the liquid surface of the solution. Then, the pH is adjusted with an appropriate acid alkaline solution. Because the PBLH membrane surface is positively charged, the native ferritin 21 which is negatively charged is attached on the PBLH membrane.
Next, in the step shown in FIG. 1C, a base material (silicon substrate) 40 which had been subjected to a hydrophobic surface treatment is floated on the liquid surface on which the PBLH membrane 30 was overlaid, thereby allowing the PBLH membrane 30 on which the native ferritin 21 is attached to be adhered on the base material.
Next, in the step shown in FIG. 1D, the silicon substrate 40 having the adhered PBLH membrane 30 on which the native ferritin 21 is attached is removed from the water bath.
Next, in the step shown in FIG. 1E, after covering the surface on which the native ferritin 21 is attached with a buffer solution 11, ultraviolet irradiation is performed using a mask pattern 50. The native ferritin in the region on which ultraviolet ray was irradiated is decomposed, and dispersed in the solution.
Next, in the step shown in FIG. 1F, the silicon substrate 40 after executing the patterning shown in FIG. 1E is washed with water.
Next, in the step shown in FIG. 1G, the silicon substrate 40 is dried to obtain the pattern arrangement of the native ferritin including the inorganic particle therein.
Thereafter, in the step shown in FIG. 1H, a heat treatment at 500° C. is carried out in an inert gas 60 (for example, in nitrogen) to bake the native ferritin 21 including the inorganic particle therein and the PBLH membrane 30, thereby providing secondary pattern arrangement of the inorganic particles on the base material surface. This structure is further processed to give a structure required for the device as described above.
However, the SAM membrane is formed on the base material side, and patterning is executed on the SAM membrane using ultraviolet ray, or an LB membrane that is an adsorption membrane of the inorganic particle is utilized as the intermediate layer with respect to the a base material in the aforementioned conventional method. Therefore, there are possibilities that the steps may be complicated, or that impurities included in the constituents of the SAM membrane or the LB membrane, or in the solution remain on the arranged surface of the inorganic particles whereby causing adverse influences on the device.
Accordingly, an object of the present invention is to provide a technique for selectively and regularly arranging inorganic particles, in particular, those having a diameter of several to several ten nanometers in a necessary region and in a necessary amount with high mass productivity at low costs by allowing the inorganic particle to have a base material recognizing ability.